Air tools are commonly used to apply torque during make up of fastener joints. Nutrunner air tools, for example, are used to provide relative rotation between a nut and bolt by running the nut along the bolt to form a fastener joint connection. The torque applied is substantially increased under load as the fastener connection approaches completion. In order to apply a specified torque, torque shut off valves have been used in air tools to shut off the air supply to the tool motor when a desired torque specification is achieved.
To ensure that the fastener joints assembled fall within an acceptable torque specification range, regulators have been used to control the air tool pressure. Regulators operate to reduce tool air pressure, and thus operate the tool more slowly. Operation at the slower rate enables the air tool to be shut off with less risk of overshooting or missing the desired torque specification.
The critical nature of certain fastener joints additionally requires verification that the torque specification of each joint is within an acceptable range of torque specifications. Verification, or monitoring, systems are used to set a desired torque specification, and to measure the torque applied to the assembled joints to ensure they fall within the accepted range. Verification is necessary in critical fastener joints due to the numerous factors which can potentially vary the conditions of fastener joint assembly, and thus the torque specification of the fastener joint connection. Factors contributing to such variations include joint characteristics, fluctuation in air supply pressures, damage to the tool itself, the differing characteristics of fasteners, and the shut off control over the air tool valves.
One problem with existing regulators and monitoring systems is that they do not provide automatic adjustment or control over the air tool to correct future fastener joint assembly, if the measured torque specification is found to be unacceptable.